Silicon alloying of TiN has been performed by CVD from TiCl 4 -SiH 2 Cl 2 -NH 3 or N 2 -H 2 at temperatures between 850 °C and 1100 °C. With ammonia, only triphased coatings have been deposited, corresponding to TiSi 2 -Ti 5 Si 3 (N)-TiN and TiSi 2 -a Si 3 N 4 -TiN mixtures. With nitrogen, the incorporation of TiSi 2 -Ti 5 Si 3 (N) or only Ti 5 Si 3 (N) in a TiN matrix has been achieved. The influence of precursors and experimental parameters on the phase composition of the coatings has been reported. Microstrains and apparent grain sizes have been calculated from X-ray diffraction (XRD) peak broadening. Coating hardnesses ranging from 17 to 26 GPa have been related to the apparent grain size of TiN but strong correlations with microstrains or with the quantity of the incorporated titanium silicides have never been evidenced. Using an indentation fracture technique an enhancement of the composite coating toughness has been observed. It has been shown that the co-deposits have an improved oxidation resistance especially below 950 °C in comparison with TiN coatings.